1. Technical Field
The present invention generally relates to a column driving circuit and method for driving pixels in a column row matrix. More particularly, the present invention relates to an improved circuit and method for reducing the capacitive load on the columns of the matrix to provide improved pixel driving.
2. Background Art
In video displays, matrices are commonly utilized in which pixels are oriented in a column row format. The column driving scheme currently employed to drive the pixels is based on a common analog ramp signal that is sampled by all columns in the display. Problems associated with this architecture include a high capacitive load that each column presents to the column buffer, where a buffer amplifier is used in every column. Moreover, as the addressing frequency increases, as a result of a higher frame rate or a higher pixel count of the display, the fidelity of the sampled signal decreases.
Another problem associated with the existing architecture is ramp retrace. In particular, the ramp signal in each column must retrace rapidly to an initial state in order to maximize the time available for sampling. Specifically, before the columns of the existing architecture can be driven with the analog signal, they must first be brought to an initial state or retraced. Thus, driving the pixels is at least a two step process in which each column must: (1) retrace to initial state; and (2) apply the analog signal. Since, a fast retrace requires large current capability of the driver(s), the associated large transients in the matrix could cause undesired effects, e.g., activating unselected rows.
In view of the foregoing, there exists a need for a column driving circuit and method for reducing the capacitive load in the columns of the matrix. Moreover, a need exists for a column driving circuit and method that reduces the problems associated with ramp retrace.
The present invention addresses the problems of the existing architecture by providing an improved column driving circuit and method for driving pixels in a column row matrix. Specifically, the present invention provides a column driving circuit wherein each column is split into at least two column lines. Each column line communicates with/is joined to a unique subset of rows in the matrix. By splitting the columns into multiple column lines, the capacitance of each line is a fraction of that required by a single column. In addition, because each column is split into at least two column lines, a first column line can be retraced to the initial state while the second column line is being driven by the analog signal thus, reducing the delays associated with ramp retrace.
According to a first aspect of the present invention, a column driving circuit for driving pixels in a column row matrix is provided. The circuit comprises: (1) a multiplexing circuit for receiving a signal; and (2) a first and a second column line, wherein the column lines receive the signal from the multiplexing circuit, and wherein the first column line is in communication with different rows of the matrix than the second column line.
According to a second aspect of the present invention, a column driving circuit for driving pixels in a column row matrix is provided. The circuit comprises: (1) a DAC (digital to analog converter) for generating an analog signal in response to a digital input; (2) a multiplexing circuit for receiving the signal from the DAC; (3) a first and a second column line, wherein the column lines alternate in receiving the signal from the multiplexing circuit; and (4) wherein each column line includes at least one junction for communicating with a unique subset of rows in the matrix.
According to a third aspect of the present invention, a method for driving pixels in a column row matrix is provided. The method comprises the steps of: (1) receiving a signal in a multiplexing circuit; (2) selectively sending the signal from the multiplexing circuit to a first and second column line; and (3) communicating the column lines with rows of the matrix to drive the pixels, wherein the first column line communicates with different rows than the second column line
Therefore, the present invention provides a column driving circuit and method for driving pixels in a column row matrix. The present invention reduces the problems associated with high column capacitance and ramp retrace.